Not applicable.
Not applicable.
1. Field of the Invention
The present invention relates to the links in an infeed conveyor for conveying logs into a saw in a sawmill, and in particular, to the links in a type of conveyor known as a sharp chain.
2. Brief Description of the Related Art
A conveyor known as a sharp chain is employed in sawmills to convey and feed logs into a saw. The sharp chain is typically a link-type chain in which alternating links have upstanding spikes for engaging the log and maintaining it in a fixed orientation. These links, referred to as spiked links or dog links, are connected by pins to connecting links. The whole forms an endless chain which is sprocket-driven. The endless chain passes around at least one infeed sprocket gear and at least one outfeed sprocket gear.
Examples of sharp chains are disclosed in U.S. Pat. Nos. 4,881,584; 5,765,617; 6,062,281; and 5,385,186.
An early form of spiked link for a sharp chain is disclosed in U.S. Pat. No. 4,886,156 to Records et al: In this style of sharp chain, the spiked link has a single leg which rides in a V-shaped guide. Lateral stability can be a problem with this type of link, which has been mostly supplanted by an H-style link. The H-style link has two legs connected by a centrally-located saddle. The H-style link improves the lateral stability of the sharp chain. Sharp chains incorporating the H-style link typically are driven by sprocket gears with teeth that bear against the ends of the connecting links or against the saddle. In the commonest form of spiked link, the sprocket teeth bear against the ends of the connecting links, which therefore puts considerable pressure on the pins that connect the connecting links to the spiked links. Since the pins have limited bearing area and are further subject to wear from rotational motion of the links as they pass around the sprocket gears, failures to the pins and the ends of the connecting links are a common problem.
An additional problem with the H-style spiked link is that the legs on either side of the saddle tend to exhibit excessive flexibility as a result of the central placement of the saddle and the limited rigidity that the relatively small saddle imparts to the spiked link. Such flexibility is undesirable in that the flexing of the legs contributes to wear and consequent failure of the connecting pins and connecting links.
The limitations of the prior art are overcome by the present invention as described below.
The present invention is directed to an improvement in the design of a spiked link for a sharp chain conveyor. The spiked link of the present invention departs from the prior H-style design in that the single centrally-placed saddle is replaced by a double saddle with a centrally-located opening shaped to receive a sprocket tooth. The resulting center drive action for the spiked link avoids driving the chain from the ends of the connecting links and thus removes this source of failure for the connecting pins and connecting links.
Furthermore, the double saddle design moves each of the two saddles outward from the central portion of the spiked link. The distance between each saddle and the connecting pin is therefore reduced. This contributes to the rigidity of the legs between which the connecting pins act. With less flexion of the legs, the potential for the connecting pins to bind and wear is reduced.
A second feature of the present invention is that the legs are provided with an offset step on the inner portion of each leg. The offset step is defined by the portion of the legs where the connecting link never xe2x80x9cworksxe2x80x9d during any portion of the chain""s motion around the circuit of the sprocket gears. Since the connecting link never intrudes into this space, the offset step allows the legs in these areas to be thickened. This allows a corresponding decrease in the thickness of the legs in the region where the connecting link works. Since the width of the spiked link is fixed by the conventional size of sharp chains commonly employed in the industry, the thickness of the legs can only be decreased on the inner sides. By decreasing the thickness of the legs in the region where the connecting link works, the connecting link may be widened from the prior art connecting link. Significantly, this allows for a greater bearing surface on the connecting pin and thus reduces the rate of wear on the connecting pin and on the ends of the connecting links. By combining the thickened area of the offset steps and reducing the longitudinal distances of the legs between the saddles and the connecting pins, the legs retain sufficient stiffness and strength so that no problems are introduced by reducing the thickness of a portion of the legs to increase the bearing surface of the connecting pins.
It is therefore an object of the present invention to provide for an improved spiked link for a sharp chain conveyor in which the central saddle is replaced by a double saddle.
It is a further object of the present invention to provide for such an improved spiked link having an offset step allowing an increased width for the connecting link and a consequently greater bearing area for the connecting pin.
These and other features, objects and advantages of the present invention will become better Understood from a consideration of the following detailed description of the preferred embodiments and appended claims in conjunction with the drawings as described following: